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dds::core::policy::DurabilityKind Struct Reference

#include "PolicyKind.hpp"

Public Types

enum  Type { VOLATILE, TRANSIENT_LOCAL, TRANSIENT, PERSISTENT }
 

Detailed Description

Definition at line 54 of file PolicyKind.hpp.

Member Enumeration Documentation

◆ Type

enum dds::core::policy::DurabilityKind::Type
Enumerator
VOLATILE 

The samples are not available to late-joining DataReaders. In other words, only DataReaders, which were present at the time of the writing and have subscribed to this Topic, will receive the sample. When a DataReader subscribes afterwards (late-joining), it will only be able to read the next written sample. This setting is typically used for data, which is updated quickly.

TRANSIENT_LOCAL 

Currently behaves identically to the TRANSIENT_DURABILITY_QOS, except for its RxO properties. The desired behaviour of TRANSIENT_LOCAL_DURABILITY_QOS can be achieved from the TRANSIENT_DURABILITY_QOS with the default (TRUE) setting of the autodispose_unregistered_instances flag on the DataWriter and the service_cleanup_delay set to 0 on the durability service. This is because for TRANSIENT_LOCAL, the data should only remain available for late-joining readers during the lifetime of its source writer, so it is not required to survive after its source writer has been deleted. Since the deletion of a writer implicitly unregisters all its instances, an autodispose_unregistered_instances value of TRUE will also dispose the affected data from the durability store, and thus prevent it from remaining available to late joining readers.

TRANSIENT 

Some samples are available to late-joining DataReaders (stored in memory). This means that the late-joining DataReaders are able to read these previously written samples. The DataReader does not necessarily have to exist at the time of writing. Not all samples are stored (depending on QosPolicy History and QosPolicy resource_limits). The storage does not depend on the DataWriter and will outlive the DataWriter. This may be used to implement reallocation of applications because the data is saved in the Data Distribution Service (not in the DataWriter). This setting is typically used for state related information of an application. In this case also the DurabilityServiceQosPolicy settings are relevant for the behaviour of the Data Distribution Service.

PERSISTENT 

The data is stored in permanent storage (e.g. hard disk). This means that the samples are also available after a system restart. The samples not only outlives the DataWriters, but even the Data Distribution Service and the system. This setting is typically used for attributes and settings for an application or the system. In this case also the DurabilityServiceQosPolicy settings are relevant for the behaviour of the Data Distribution Service.

Definition at line 56 of file PolicyKind.hpp.

The documentation for this struct was generated from the following file: